let age:number = 90
let username:string = 'lisi'
let isSameColor: boolean = false
let arr:Array<string> = ['lisi','zs']
let add = (a:number,b:number):number=>a+b
function sayHello():void{
    console.log('hello');
}
let x:number = add(3,4)
console.log(x);
sayHello()